Formation and Decomposition of Trialkyllead Compounds in the Atmosphere

Abstract

The kinetics and mechanisms of the homogeneous reactions of tetramethyllead (TML) and tetraethyllead (TEL) with hydroxyl (HO) have been studied. A suite of lead products were found, including ionic trialkyllead (TriAL) and dialkyllead (DiAL) compounds and inorganic Pb. The ionic alkyllead products were found both in the gas phase and in the aerosol, as well as on the reaction chamber walls. The decomposition reactions of TML, TEL, and the ionic trimethyllead and triethyllead salts were found to proceed with pseudo-first-order kinetics, with the ionic TriAL compounds being about 3 times less reactive with HO than the corresponding tetraalkyllead (TAL) compounds. The ionic TriAL compounds are therefore quite persistent in the atmosphere, ionic TriML having a global mean half-life of about 5 days. The observed occurrence of ionic alkyllead compounds in the atmosphere is therefore explicable in terms of their atmospheric chemistry. © 1986, American Chemical Society. All rights reserved.